1. Field
The present invention relates generally to improved method and apparatus for identifying objects. Still more particularly, the present invention relates to a method and apparatus for detecting objects located in the ground using electromagnetic radiation.
2. Background
An increasing demand is present for an approach to detect and locate tunnels, underground infrastructure, and for identifying objects located within the ground. A threat is posed by tunneling. Tunnels may be deeply bored. Deep urban bunkers with interconnecting tunnels also may be present. These types of tunnels are often used to smuggle illegal contraband into and out of a country. Many of these facilities are deeply buried or significantly hardened in an attempt to preclude detection and characterization by sensors.
Various approaches that have been considered for detecting tunnels include electromagnetic and gravity gradiometry, thermal, seismic, or other nondestructive and noninvasive investigations. These approaches have been used by active and passive systems through unattended ground vehicles and unmanned aerial vehicles, as well as other land mobile platforms as mountings for these types of sensors. Invasive techniques that have been used include drilling techniques for tunnel detection and verification. With respect to detecting tunnels at different ranges, a need has developed for detecting near surface tunnels. These types of tunnels typically have a depth range anywhere between a few feet to a hundred feet or more under the surface. Currently available techniques do not have the depth range and resolution needed to detect tunnels at the deeper end of this depth range.